This invention relates to a novel chemical additive and method for use in an ammunition propellant system for reducing gun barrel thermal erosion, smoke and flash.
Gun barrel erosion has long been a problem with high flame temperature ammunition propellants and has become more difficult to solve as rates of fire are increased. Extended range requirements mandate the use of larger charges and higher flame temperature propellants. The combination of these conditions results in extreme conditions of gun barrel wear. Theoretically, gun barrel wear can be reduced by protecting the interior surface of the gun barrel against erosive action of the hot propellant gases. It is necessary to use inexpensive chemical additives to reduce gun barrel wear since tremendous quantities of artillery and tank ammunition propelling charges are manufactured for ordnance use.
Various materials have previously been suggested as wear reducing additives. In U.S. Pat. No. 3,148,620, Jacobson et al. disclosed a cartridge with a propellant charge and single projectile having a wear reducing additive comprising a layer of paraffin carrier material disposed around the charges having finely divided titanium dioxide in an amount to produce a temperature resistant barrel "protection" upon firing. Picard teaches that wear and erosion of gun members can be reduced when silicates (U.S. Pat. No. 3,392,669) and inorganic additive consisting of silica dioxide, magnesium oxide or mixtures thereof in the form of natural talc (U.S. Pat. No. 3,392,670) are added, respectively, to propellant systems.
In U.S. Pat. No. 3,362,328, Katz discloses that fibers of polyester, acrylic, silk, wool, glass and asbestos in a wax dispersion containing calcium sulfate, calcium carbonate, a calcium sulfate and titanium dioxide mixture, and a mixture of calcium carbonate and titanium dioxide can be applied to sheets in a propellant system to reduce wear and erosion.
The prior art methods of reducing wear all relate to the use of inorganic active ingredients which are costly, not readily available and which affect propellant performance. The instant invention relates to the use of an inexpensive and readily available organic material, i.e., a starch modified copolymer which has the ability to absorb many times its own weight in water with or without glycol, to reduce wear of gun members coming into contact with hot gases generated by propellant ignition.